The present invention generally relates to the degating of molded parts from a runner and more particularly to a system and method for removing from a molding tool a plurality of molded parts that are connected to a runner via gates and subsequently degating the plurality of molded parts from said runner in a single phase operation.
The injection molding of thermoplastic molded parts typically involves the injection of molten thermoplastic material into a mold that provides for the connection of a plurality of molded parts to a runner, referred to herein as a xe2x80x9crunner assembly.xe2x80x9d By molding the runner assembly so that the molded parts are connected to a runner, the molded parts may be removed from the mold at one time by simply removing the runner assembly. This eliminates the need to remove the molded parts individually, and thus increases throughput. Typically, each of the molded parts is connected to the runner via a gate, which is a thin or narrow portion of the thermoplastic material. After the runner assembly is removed from the molding tool, the molded parts may be separated from the runner by cutting, breaking or melting the gate.
The separation of molded parts from runners through the introduction of ultrasonic energy into the gate is referred to as ultrasonic degating. Sources of ultrasonic energy include ultrasonic horns which, when positioned suitably close to the runners, ultrasonically excite the gates by producing mechanical vibrations in the runner. The mechanical vibrations generate a standing wave of energy down the runner through the gate and into the molded part, which resonates. The freely resonating part goes through a cyclic bending moment with the gate which induces stress into the gate and generates internal molecular friction. The internal molecular friction raises the temperature of the gates. When the melting temperature of the gate is reached, the molded part is separated from the runner.
The removal of the runner assembly from the molding tool and the degating of the molded parts from the runner are typically performed during a multiple phase operation. First, the runner is removed from the molded tool manually by a first automatic holder and stored in a collection unit. The runner assembly may then be removed from the collection unit and manually or mechanically positioned in a second holder proximate to an ultrasonic horn for degating. Alternatively, the runner assembly may be manually or mechanically placed on a conveyor belt after removal from the molding tool and transferred from the molded tool to the ultrasonic horn. The runner assembly may then be manually or mechanically positioned in a second holder for degating. However, this multiple phase operation limits throughput of the injection molding process. In addition, because of the handling of the runner assembly by multiple holders, the multiple phase operation risks breaking of the runner assembly. Further, multiple phase operations are typically expensive due to the additional hardware and tooling required to facilitate the multiple phases of operation.
Accordingly, there is a need for a system and method for removing from a molding tool a runner assembly and subsequently degating the molded parts from the runner of the runner assembly in a single operation.
This summary of the invention section is intended to introduce the reader to aspects of the invention and is not a complete description of the invention. Particular aspects of the invention are pointed out in other sections hereinbelow, and the invention is set forth in the appended claims which alone demarcate its scope.
In accordance with an exemplary embodiment of the present invention, a system for removing from a molding tool a runner assembly having a plurality of molded parts that are connected to a runner via gates and subsequently degating the plurality of molded parts from the runner is provided. The system includes a source of ultrasonic energy and a robot arm assembly. The robot arm assembly is configured to remove the runner assembly from the molding tool and to position the runner assembly proximate the source of ultrasonic energy.
In accordance with another exemplary embodiment of the present invention, a method for degating a plurality of molded parts that are connected to a runner via gates is provided. The method includes causing a robot arm assembly to position the plurality of molded parts and the runner proximate to a source of ultrasonic energy. The method also includes pressing the runner against the source of ultrasonic energy. The method further includes activating the source of ultrasonic energy so that the plurality of molded parts is degated from the runner.
In accordance with a further exemplary embodiment of the present invention, a robot arm assembly for holding a runner assembly comprising a plurality of molded parts and a runner connected thereto during degating of the plurality of molded parts from the runner is provided. The robot arm assembly includes a robot arm configured to transport the runner assembly from a molding tool to a source of ultrasonic energy. The robot arm assembly also includes a carrier assembly configured to hold the runner assembly.
These and other aspects of the present invention are described in the following description, attached drawings and claims.